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AQA iGCSE Physics > 1. Forces and their effects > Flashcards

1. Forces and their effects Flashcards

1
Q

What is the conservation of momentum?

A

The idea that in a closed system, the total momentum before an event = total momentum after the event

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2
Q

How do safety features like air bags, seat belts and cushioned surfaces work?

A

Increase the impact time

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3
Q

p = m x v

A

Momentum (kgm/s) = Mass (kg) x velocity (m/s)

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4
Q

What are scalar quantities?

A

Quantities that have magnitude only

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5
Q

What are vector quantities?

A

Quantities that have magnitude in a given direction

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6
Q

What is velocity?

A

Speed in a given direction

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7
Q

Distance time-graph

A

The gradient of it is the speed, if accelerating use a tangent to find the gradient

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8
Q

Velocity-time graph

A

The gradient gives the acceleration

Area under the graph equals the distance travelled

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9
Q

v = s/t

A

Velocity(m/s) = Displacement (m) / Time (s)

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10
Q

a = (v– u)/t

A

Acceleration (m/s/s) = (Final velocity(m/s) - Initial Velocity (m/s)) / Time (s)

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11
Q

What is referred to as “Elastic Behaviour”?

A

When a force acts on an object it may cause a change in shape, the object behaves Elastically if it returns to its original shape when the force is removed

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12
Q

What happens when you apply force to an elastic object?

A

The object stretches and stores elastic potential energy

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13
Q

For an object behaving elastically, what is the extension is directly proportional to?

A

The force applied

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14
Q

F = k x e

A

Force (N) = Spring constant x Extension (cm)

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15
Q

The faster an object moves through a fluid the greater what is?

A

The greater the frictional force that acts upon it

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16
Q

Terminal velocity

A

An object falling through a fluid will initially accelerate due to gravity
Eventually the friction will be the same as the downwards forces
The resultant force will equal zero and the object will move at its terminal velocity (greatest steady speed)

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17
Q

Whenever two objects interact…

A

The forces they exert are equal and opposite

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18
Q

Resultant forces

A

A resultant force as a single force obtained by combining a system of forces on a single body

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19
Q

If the resultant force acting upon a stationary object is:

A

Zero, the object will remain stationary

Not zero, the object will accelerate in the direction of the resultant force

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20
Q

If the resultant force acting on a moving object is:

A

Zero, the object will continue to move at the same speed and direction

Not zero, the object will accelerate in the direction of the resultant force

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21
Q

What are the resistive forces when driving?

A

Air resistance and friction

When a car travels at a steady speed the resistive forces balance the driving forces

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22
Q

The greater the speed the greater the braking force needed to stop it in a certain distance

A

For a given braking force, the greater the speed the greater the stopping distance

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23
Q

What is the stopping distance?

A

The thinking distance + The braking distance

24
Q

What affects the drivers reaction time?

A

Tiredness, drugs, alcohol, (distractions)

25
Q

What happens when the brakes are applied?

A

Work done by friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increases

26
Q

What can affect the vehicles braking distance?

A

Poor road, weather (icy & wet) & vehicle (brakes and tyres) condition

27
Q

F = ∆p / T

A

Force (N) = Change in momentum (Kgm/s) / Time (s)

28
Q

F = m x a

A

Force (N) = Mass (kg) x Acceleration (m/s/s)

29
Q

W = m x g

A

Weight(N) = Mass(kg) x Gravitational field strength

30
Q

W = F x d

A

Work done (J) = Force (N) x Distance moved in Direction of force (m)

31
Q

P = W / t

A

Power (Watts) = Work done (J) / Time (s)

32
Q

Ep = m x g x h

A

Change in gravitational potential energy = Mass x Gravitational field strength x Change in height

33
Q

Ek = 1/2 x m x v^2

A

Kinetic Energy = 1/2 x Mass(kg) x Velocity^2

34
Q

Work is done when a force causes an object to move through a distance

A

Energy is transferred when work is done

35
Q

What does Work Done against frictional forces cause?

A

Energy transfer by Heating

36
Q

What happens when an obstacle is lifted vertically up?

A

Work is done against gravity and the object gains gravitational potential energy

37
Q

What will happen to the Kinetic energy if an object with double the mass of another object travels at the same speed?

A

The Kinetic Energy is doubled

38
Q

What will happen to the Kinetic energy if an object the same mass as another object travels at double the speed?

A

The Kinetic Energy will be four times greater

39
Q

What is the centre of mass?

A

The point at which the mass of the object is thought to be concentrated

40
Q

Where is the centre of mass of symmetrical objects?

A

Along the axis of symmetry

41
Q

Where will the centre of mass be of an object freely suspended ?

A

Directly below the point of suspension

42
Q

What does the time period of a pendulum depend on?

A

The length of the pendulum

43
Q

Applications of pendulums

A

Simple fairground and playground rides

44
Q

T = 1 / f

A

Time period = 1 / frequency

45
Q

What is a moment?

A

A moment is a turning effect of a force around a fixed point called a pivot

46
Q

What does a moment depend on?

A

The size of the force applied

The perpendicular distance from the pivot to the line of action of the force

47
Q

What can simple levers be used as?

A

Force multipliers

48
Q

What happens if the line of action of the weight of an object lies outside the base of the object?

A

There will be a resultant moment and the body will topple

49
Q

Useful uses of Moments?

A

Cranes, tools such as hammers and balancing toys

50
Q

M = F x D

A

Moment (Newton-Metres) = Force (Newtons) X Perpendicular Distance (Metres)

51
Q

Hydraulics

A

Liquids are cutely incompressible and the pressure in a liquid is transferred equally in all directions

52
Q

How do Hydraulics work as force multipliers?

A

P = F/A
the pressure in a liquid remains constant so, indoor to keep the same pressure, if the cross sectional surface area increases the force must increase with it

53
Q

P = F / A

A

Pressure (Pascals, Pa) = Force (Newtons) / Cross-sectional area (m^2)

54
Q

What happens with an object moves in a circle?

A

It is continuously accelerating towards the centre of the circle, as its velocity is changing not its speed

55
Q

What is centripetal force?

A

The resultant force causing the acceleration seen in circular motion
It always acts directly towards to centre

56
Q

Centripetal force needed to make an object perform circular motion include:

A

The mass of the object increasing
The speed of the object increasing
The radius of the circle decreasing

AQA iGCSE Physics (6 decks)

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